Answer:
10+4x+11=x²-10+10 (add 10 both side)
21+4x-4x=x^2-4x (substract 4x in both side)
21-21=x^2-4x-21 (substract 21 in both side)
x^2-4x-21=0
x^2+3x-7x-21=0(we can write -4x as (3x)+(-7x)=(-4x)
x(x+3)-7(x+3)=0 (get common factor)
(x+3)(x-7)=0 (get common factor which is (x+3) by both)
x=-3 or x=7
Explanation: